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1.2 Synchronous Motors Synchronous motors, as the name implies, rotate at a constant (synchronous) speed. The rotor of this type of motor is a wound rotor, which receives the excitation (magnetizing) current from its excitation system (a separate direct current source with controller).
Why a synchronous motor is named so?
Definition: The motor which runs at synchronous speed is known as the synchronous motor. The synchronous speed is the constant speed at which the motor generates the electromotive force. The synchronous motor is used for converting the electrical energy into mechanical energy.
What is a 3 phase synchronous motor?
The three-phase synchronous motor is a unique and specialized motor. As the name suggests, this motor runs at a constant speed from no load to full load in synchronism with line frequency. This attraction exerts a torque on the rotor and causes it to rotate at the synchronous speed of the rotating stator field.
What are the types of 3 phase synchronous motor?
This type of synchronous motor is divided into three categories and is available in three designs, each of which has unique features: Hysteresis Synchronous Motors. Reluctance Synchronous Motors. Permanent Magnet Synchronous Motors.
Why are synchronous generators called synchronous?
A synchronous generator is called “synchronous” because the waveform of the generated voltage is synchronized with the rotation of the generator. Each peak of the sinusoidal waveform corresponds to a physical position of the rotor. The magnetic field of the rotor is supplied by direct current or permanent magnets.
How can synchronous motor be stopped?
The methods that are employed for Braking of Synchronous Motor are: Regenerative braking while operating on a variable frequency supply. Rheostatic braking. Plugging.
What are the advantages of synchronous motor?
Advantage or Merits: One of the major advantage of using synchronous motor is the ability to control the power factor. An over excited synchronous motor can have leading power factor and can be operated in parallel to induction motors and other lagging power factor loads thereby improving the system power factor.
Why synchronous motors are not self-starting?
Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator. Once the rotor nears the synchronous speed, the field winding is excited, and the motor pulls into synchronization.
Which synchronous motor will be smallest in size?
Which synchronous motor will be smallest in size ? (D) 10 HP, 375 rpm. Explanation: Q15.
Why the speed of synchronous motor is constant?
When you supply 60 Hz (or 50 Hz), the motor will spin at one speed, which is dependent on the number of poles. This rotational speed will be constant with different mechanical loads, up to the point that the motor (or coupling) fails, hence it is a “constant speed” motor.
Is 3 phase induction motor is self-starting?
Three-phase induction motor is self-starting, because winding displacement is 120 degrees for each phase and supply also has 120 phase shift for 3-phase. It results in a unidirectional rotating magnetic field is developed in air gap which causes 3-phase induction motor to self-start.
What is the principle of synchronous motor?
The principle of operation of a synchronous motor can be understood by considering the stator windings to be connected to a three-phase alternating-current supply. The effect of the stator current is to establish a magnetic field rotating at 120 f/p revolutions per minute for a frequency of f hertz and for p poles.
What are the two types of synchronous generators?
Types of synchronous machines Hydrogenerators : The generators which are driven by hydraulic turbines are called hydrogenerators. These are run at lower speeds less than 1000 rpm. Turbogenerators: These are the generators driven by steam turbines. Engine driven Generators: These are driven by IC engines.
What is the function of synchronous generator?
Definition: The synchronous generator or alternator is an electrical machine that converts the mechanical power from a prime mover into an AC electrical power at a particular voltage and frequency. The synchronous motor always runs at a constant speed called synchronous speed.
Why do we use synchronous generator?
Synchronous generators are the majority source of commercial electrical energy. They are commonly used to convert the mechanical power output of steam turbines, gas turbines, reciprocating engines and hydro turbines into electrical power for the grid. The load supplied by the generator determines the voltage.
How does a synchronous motor start?
The motor is first started as a slip ring induction motor. The resistance is gradually cut-off as the motor gains speed. When it achieves near synchronous speed, DC excitation is given to the rotor, and it is pulled into synchronism. Then it starts rotating as a synchronous motor.
What is the speed of synchronous motor?
Synchronous speed is the speed of rotation of the magnetic field in a rotary machine. An induction motor always runs at a speed less than synchronous speed. The rotating magnetic field which is produced in the stator will generate flux in the rotor which will make the rotor rotate.
What is the application of synchronous motor?
Synchronous motors are normally used in applications in which a constant and precise speed is required. Typical applications of these low power motors are positioning machines. They are also used in robot actuators. Synchronous motors are also used in ball mills, watches, record players, and turntables.
What is the advantage of synchronous current?
The advantages of the synchronous motor are the ease with which the power factor can be controlled and the constant rotational speed of the machine, irrespective of the applied load. Synchronous motors, however, are generally more expensive and a d.c. supply is a necessary feature of the rotor excitation.
What is the difference between asynchronous motor and synchronous motor?
Synchronous motor is a machine whose rotor speed and the speed of the stator magnetic field is equal. Asynchronous motor is a machine whose rotor rotates at the speed less than the synchronous speed. Asynchronous motor does not require any additional starting source.
What are the main characteristics of synchronous motor?
Main Features of Synchronous Motors Synchronous motors are inherently not self starting. The speed of operation of is in synchronism with the supply frequency and hence for constant supply frequency they behave as constant speed motor irrespective of load condition.
